Operation Manual

Chapter 17: Activities 308

Graphing Inequalities

Problem

Graph the inequality 0.4x

N 3x + 5 < 0.2x + 4. Use the TEST menu operations to explore the values of X

where the inequality is true and where it is false.

Note: You can also investigate graphing inequalities using the Inequality Graphing application. The

application is pre-loaded on your TI-84 Plus C and can be downloaded from education.ti.com.

Procedure

1. Press z. Select Dot-Thick, Simul, and the default settings. Setting Dot-Thick mode changes all

graph style icons to (Dot-Thick) in the

Y= editor.

2. Press o. Turn off all functions and stat plots. Enter the left side of the inequality as Y4 and the right

side as Y5.

3. Enter the statement of the inequality as Y6. This function evaluates to 1 if true or 0 if false.

Note: You can use the YVARS shortcut menu (ƒ a) to paste Y4 and Y5 in the Y= editor.

4. Press q

6:ZStandard to graph the inequality in the standard window.

5. Press r † † to move to

Y6. Then press | and ~ to trace the inequality, observing the value of

When you trace, you can see that Y=1 indicates that Y4<Y5 is true and that Y=0 indicates that

Y4<Y5 is false.

6. Press o. Turn off

Y4, Y5, and Y6. Enter equations to graph only the inequality.